In the field of passenger information systems more and more high resolution screens are being installed on board of trains, trams and light rail vehicles. These panels are replacing lower resolution matrix displays, e.g. LED displays. This trend is facilitated by the increased robustness of these high resolution panels. In addition, these visualization devices are now available in different sizes. This eases the integration in the passenger area of rail vehicles. Another enabler for this tendency is the fact that embedded processors have become much more powerful and that they are now capable to drive these high resolution output devices.
The main advantage is that these high resolution displays (implemented as e.g. plasma or TFT screens) are capable of communicating more information in an accessible way to passengers compared to other, older communication means.
The basic set-up of such a system is depicted in FIG. 1. A video source (100) renders the data to be visualized on the display (200) using a video link (105). In an advantageous implementation the video source is an (embedded) processor. Other possible implementations can be in FPGA, Video Integrated Circuit, Application Specific Integrated Circuit or by means of other digital video sources. In the majority of applications, the video source (100) is connected by means of one or more communication channels to an on board network (700). Via this network context data and/or data to be visualized are pushed towards the visualization engine (100). The number of tasks to be fulfilled by this video source is typically substantial. A non-exhaustive list includes rendering of templates, decoding JPEG images, decoding of high resolution movie streams, layering, font rendering and handling of network communication. These tasks increase the processor load extensively.
Some information to be shown will scroll over a certain area of the display. The primary advantage of scrolling particular data is the ability to display a larger amount of information than when stationary data is used. As the data moves across a limited space, more information can be displayed and a constantly changing message is presented to readers. Another advantage of scrolling information is that it is more attention-grabbing than stationary data.
The data referred to is not restricted to plain text only (e.g. announcing the next stations on a certain route), but can be various kinds of visual data (e.g. a logo, picture, icon, . . . ).
In addition, some applications require several areas that scroll data, referred to as scrolling banners in the remainder of this description.
In order to implement a smooth scrolling banner the following process is required. At first, the video source needs to render the data to be scrolled within the banner area. This can include font rendering, picture drawing, and so forth. As soon this is finished, in a second phase this data is copied or moved to the memory of the device in charge of the scrolling. This can be the render engine itself or an external device. In a last, third stage the device needs to correctly start the scrolling and ensure that the movement is as smooth as possible over time.
However, some technical difficulties arise when one wants to take into account these three steps in order to realise smooth scrolling banner(s) on the visualization area while at the same time keeping the processor load at an acceptable level. In FIG. 2 different frames are being depicted to be visualized on the screen. In typical applications every frame is visualized for approximately 16 ms. This time interval is referred to as the period of the display's frame rate. In FIG. 2 frame j might, for example, visualize some movie or other graphics (711). Frame j+1 is completely different and includes a banner area (712). The banner should not be visualized in the preceding frame j. The information scrolls until frame n and the banner should disappear immediately in frame n+1. Therefore, synchronization between the visualization of the banner area and the rest of the screen should be handled on frame level. The arrow (900) in FIG. 3 visualizes the direction wherein the data to be visualized should move.
In addition, to allow the second phase in the process to implement smooth scrolling, the video source should have access to a high bandwidth communication channel (124) to allow copying the area to be scrolled over time to storage means (800) of the scrolling device as depicted in FIG. 4. Providing such a high bandwidth communication channel (124), however, involves an additional cost and requires additional processor power.
Beside the capability to allow transparent scrolling (i.e. scrolling whereby data content is overlaid on top of other data content, which also remains at least partially visible), as depicted in FIG. 3, it is an absolute requirement to ensure a consistent smooth movement of the data over the screen per time. No hiccups (i.e. halting of movement during a short or longer period of time) are tolerated. The number of pixels moved per frame must therefore be kept constant at all times.
In the art solutions are known for embedded hardware acceleration in microprocessors. However, absolute smooth scrolling (defined as a consistent movement of data in a certain direction per frame) is not feasible with current solutions. These high end processors cannot be applied in applications where limited heat and power dissipation is required.
In WO2008/004189 a method is disclosed of transmitting a TV signal including an information ticker. A ticker refers to a scrolling display wherein new data or information appears and enters a display area at one end of the display screen (typically, the right hand side) and scrolls across the display screen to the opposite end (typically the left hand side) where it departs the screen. Examples of tickers include news tickers, stoke quote tickers and so on. The proposed solution overcomes the limitations of known ticker solutions that do not offer any flexibility in dealing with the ticker data on the user side. According to the disclosure of WO2008/004189 first ticker data is embedded in a video stream and second ticker data in a separate data stream. The video stream and separate data stream are next multiplexed and broadcasted in a television signal. The proposed solution allows the end user, i.e. the TV viewer, to deal with the ticker data in a flexible way.
Hence, there is a need for a solution wherein the above-mentioned problems are overcome.